Lactosylation of milk proteins during the manufacture and storage of skim milk powders

Extensive lactosylation of milk proteins in standard skim milk powder dried against air between 185 and 90°C (inlet and outlet temperatures of the air) was detected by capillary electrophoresis. Optimisation of the drying conditions included keeping the outlet temperature low (preferably <80°C), since this was the parameter which most affected the extent of lactosylation of milk proteins. The inlet temperature was set in order to obtain the best compromise between a low extent of lactosylation and a high drying rate (170–175°C). These conditions allowed the manufacture of low-lactosylated skim milk powder. Storage of freeze-dried and control low-lactosylated skim milk powder at different temperatures showed that both temperature and moisture content affected the progress of lactosylation during storage. Further drying to less than 2.5% moisture content (w/w) and storage at low temperatures were required to prevent the development of lactosylation in the low-lactosylated skim milk powder.     

Water sorption and glass transition properties of spray dried lactose hydrolysed skim milk powder

The moisture sorption behaviour and glass transition temperature of spray dried skim milk powder with hydrolysed lactose (SMPHL) were determined. Spray drying of skim milk with hydrolysed lactose resulted in very low cyclone recovery of 25% and a large amount of powder remained stuck inside the spray dryer. The equilibrium moisture content of SMPHL was lower than that of lactose for each range of water activity when humidified for 21 days at 23 °C using saturated salt solutions. Unlike lactose, SMPHL did not lose water when the water activity exceeded 0.432 and no crystallization was noticed at water activity ?0.753. The sorption isotherm data for SMPHL fitted well with the BET and GAB models with monolayer moisture contents of 7.55 and 8.27 g/100 g, respectively. The glass transition temperature of anhydrous SMPHL was 49 °C. The critical water activity and moisture content for SMPHL were 0.15 and 2.4 g/100 g dry solid, respectively. The low critical values indicated hydrolysis of lactose necessities maintenance of very low moisture of powder for its long-term stability.     

陕西生鲜羊奶及其加工羊奶粉品质调研分析及相关性研究

为调查陕西省生鲜羊奶及羊奶粉品质随月份的变化规律,明确生鲜羊奶和羊奶粉品质之间的相关关系,该研究以2020年4月至11月某乳品企业在陕西不同地区的奶站收购的生鲜羊奶及其加工羊奶粉为试验样品,对其感官、理化和安全指标进行分析.结果表明,生鲜羊奶和羊奶粉在感官指标方面均符合国家标准要求;在理化指标方面,生鲜羊奶脂肪含量为3...     

远红外聚丙烯熔喷超细纤维非织造布的研究

研制了一种含有纳米陶瓷粉的聚丙烯熔喷超细纤维非织造布,采用电子扫描显微镜分析了该熔喷非织造布的纤网形态结构,并对其透气性、透湿性以及远红外功能等进行了测试。结果表明:加入纳米陶瓷粉之后,熔喷非织造布纤网结构变得稀疏,其透气、透湿性能都有所提高;当纳米陶瓷粉含量为8%时,聚丙烯熔喷非织造布的远红外发射率达82%,是一种优良的保暖絮片。     

Response surface optimisation of spray dryer operational parameters for low‐phenylalanine skim milk powder

The aim of this study was to optimise the spray‐drying process for low‐phenylalanine (low‐Phe) milk. Influence of inlet air temperature (100, 150 and 200 °C), feed flow rate (5, 10 and 15 mL min^?1) and air flow rate (400, 600 and 800 L h^?1) on the solubility, yield, water activity and moisture content (MC) of the milk powder were assessed using response surface methodology. The following optimum process parameters were determined: inlet air temperature of 160 °C, feed flow rate of 8 mL min^?1 and air flow rate of 400 L h^?1. The predicted values for the solubility, yield, water activity and MC were 98.77%, 88.08%, 0.263% and 5.48%, respectively. With the optimum parameters, the experimental values for the solubility, yield, water activity and MC were 97.56 ± 0.03%, 87.00 ± 0.10%, 0.26 ± 0.01% and 5.53 ± 0.08%, respectively. The similarity of the experimental results to the predicted values verified the models.     

Optimisation of spray drying process parameters for low‐fat honey‐based milk powder with antioxidant activity

The purpose of this study was to optimise process parameters to prepare spray‐dried honey‐based milk powder containing functional properties of honey. Experimental design with temperature (180 to 200 °C), honey concentration (5–15%) and feed flow rate (8–10 rpm) as independent variables was studied to investigate the effect on product responses. Results showed that increasing the temperature resulted in powder with lower moisture, bulk density, antioxidant activity, total phenolic contents, total flavonoid contents and higher water solubility index. Increasing feed flow rate resulted in higher moisture, bulk density, antioxidant activity, reduced water solubility index, total phenolic content and total flavonoid content, whereas increasing honey concentration resulted in increase in antioxidant activity, total phenolic content and total flavonoid content. The moisture content, bulk density, water solubility index, DPPH scavenging activity, total phenolic content and total flavonoid content were 3.27%, 0.44 g cc^?1, 96.67 g g^?1, 17.45%, 2.54 GAE g^?1 powder and 1.40 RE g^?1 powder, respectively.     

The effect of the water of combustion on the efficiency of direct gas-fired driers for milk powder production

Results are presented which show that the water formed during the combustion of hydrocarbon fuel is significant in relation to the evaporation potential of the fuel when used in a direct gas-fired drier. As a result, the outlet air humidity of direct-fired driers is higher than that of indirect-fired plant operating at the same outlet and inlet air temperatures. The powder moisture increases with increasing humidity at constant temperature. To compensate for this increase in moisture content, either the drier must be run at a lower inlet temperature throughout, or the outlet temperature of the drier must be increased. However, with heat sensitive materials such as milk a serious loss in powder solubility can occur if the latter action is chosen. These results suggest that the difference in overall efficiency of direct and indirect forms of heating in spray driers is less than has previously been assumed .     

Factors affecting water balance and fecal moisture content in suckling calves given dry feed.

Holstein bull calves were used to examine factors affecting water balance and fecal moisture content in suckling calves given dry feed for 2 wk from 1 wk of age. In Experiment 1 (n = 16), the shift of water balance (decreased urine volume, and increased water retention and fecal water excretion) and elevation of fecal moisture content were greatest when calf starter and Sudangrass hay were fed in addition to liquid milk replacer, compared with calves receiving only milk replacer. Intermediate changes occurred when calves were fed milk replacer and calf starter or milk replacer, calf starter, and rice straw. Water retention was correlated positively with digestible DMI and negatively with urine volume. Fecal water excretion was highly correlated with fecal DM excretion. In Experiment 2 (n = 18), water balance and fecal moisture content during wk 2 were affected by free access to calf starter and hay from wk 1. Urine volume of calves fed dry feed and milk replacer was lower than that of calves fed only milk replacer; however, when water was available in addition to dry feed, urine volume was similar to that of calves fed only milk replacer. Fecal water excretion was highly correlated with water retention rather than with fecal DM excretion, suggesting a close relationship to extracellular fluid volume. Ruminal fermentation would be an important factor affecting both water balance and fecal moisture content in suckling calves given dry feed.     

乳粉水分含量自动控制新方法

本文采用控制喷雾干燥塔排风温度的方法来控制乳粉的含水量，通过步进电机带动干燥热风的通道挡板来改变进入喷雾干燥塔的热风量，从而控制排风温度，使乳粉的含水量控制在一定范围内，进而提高了乳粉产品的质量和生产效率。     

Effective Thermal Conductivity of Rice Flour and Whole and Skim Milk Powder

ABSTRACT: The effective thermal conductivity for 3 kinds of powdered food (rice flour, whole milk powder, and skim milk powder) was measured at selected moisture contents, temperatures, and bulk densities. The transient heat probe method using twin probes was used for the determination of the effective thermal conductivity. The effects of moisture content, temperature, and bulk density on the effective thermal conductivity of samples were investigated. The observed values were compared with the values calculated from the thermal conductivity of air and powder, using the 3 kinds of structural model for thermal conductivity, that is, the series, parallel, and random heat transfer models. An improved random heat transfer model, in which a correction term was incorporated in the random heat transfer model, with the term written as a function of moisture content and temperature, was developed.     

Color in Concentrated Milk Proteins with High Sucrose as Affected by Glucose Replacement

A model system of sucrose, whole dry milk powder, and distilled water was used to evaluate color development during heating. Sucrose replacement by glucose and moisture were the selected variables in a second-order central composite design. The main color response was the Kubelka-Munk index K/S calculated from reflectance colorimetric measurement using the Self-Backing Reflectance Transformation (SBRT) procedure. Browning reached a zone of maximum K/S when sucrose replacement increased. Additional replacement in the maximum zone did not increase browning, but produced an opposite effect decreasing browning, depending on moisture content. Chromophore group formation was higher between 40 and 75% of sucrose replacement by glucose and at 20-30% moisture content.     

微波膨化板栗脆片的工艺研究

实验以板栗粉为主要原料,加入适量的白砂糖、食盐、蛋黄粉以及NaHCO3,采用热风干燥与微波相结合的方法加工成板栗脆片,对工艺过程的主要参数进行了研究。结果表明:最佳加水量为板栗粉∶水为1∶1(g∶mL);配料的最佳配方为白砂糖6%、食盐1%、蛋黄粉5%;NaHCO3的添加量为2.0%;热风干燥初始水分含量为16%左右;微波功率为800W;微波处理时间为90s。     

不同乳基婴幼儿配方乳粉的理化性质和表面组成

为探究不同乳基对婴幼儿配方乳粉稳定性的影响,本研究对以牛乳和羊乳为基料制备的婴幼儿配方乳粉的水分质量分数和水分活度(water activity,a_w)、玻璃化转变温度(glass transition temperature,T_g)、乳糖结晶度、溶解度、色度、蛋白组成、总脂肪酸和表面游离脂肪酸组成等理化性质进行分析,用X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)仪对乳粉表面成分进行测定,并通过扫描电子显微镜(scanning electron microscopy,SEM)观察乳粉表面形貌。结果表明：羊乳婴幼儿配方乳粉具有较好的理化性质,与牛乳婴儿配方乳粉相比具有较低的水分质量分数、a_w、色度和T_g,而结晶度和溶解度接近,通过气相色谱-质谱(gas chromatography-mass spectrometry,GC-MS)对脂肪酸含量进行测定发现,牛乳和羊乳婴幼儿配方乳粉均表现出总脂肪酸中不饱和脂肪酸含量较高,表面游离脂肪酸中饱和脂肪酸含量较高的...     

Fish oil microencapsulation as influenced by spray dryer operational variables

The effects of spray‐drying air temperature, aspirator rate (drying air mass flow rate), peristaltic pump rate (feed mass flow rate) and spraying air mass flow rate on microencapsulation properties of fish oil including moisture content, particle size, bulk density, encapsulation efficiency and peroxide were investigated. The process was carried out on a mini spray dryer, and skim milk powder was used as the encapsulating wall material. Results indicated that increasing inlet air temperature increased the particle size, encapsulation efficiency and peroxide value but decreased the bulk density and moisture content of product. Increasing aspirator rate resulted in increased particle size and peroxide value but decreased the moisture content and bulk density. Increase in feed mass flow rate increased the moisture content, particle size, bulk density and peroxide value but decreased the encapsulation efficiency of microcapsules. The encapsulation efficiency and bulk density increased with the increasing aspirator rate but moisture content, particle size and peroxide value decreased.     

喷雾干燥法制备双孢菇蛋白粉工艺优化及其营养价值评价

建立了喷雾干燥法制备双孢菇蛋白粉的工艺。以集粉率为指标,在单因素实验基础上,对进风温度、提取液蛋白质浓度、进料速率进行单因素及正交实验。结果表明:进风温度为165 ℃、提取液蛋白质浓度为40 mg/mL、进料速率为650 mL/h时,集粉率最高为38.8%。所得蛋白粉为奶白色,有鲜蘑菇香味。营养检测分析表明,双孢菇蛋白粉蛋白质含量为65.8%,碳水化合物为8.8%,粗脂肪为0.4%,粗纤维为3.8%,灰分为2.0%,水分为7.20%;氨基酸种类齐全,人体必需的8种氨基酸占氨基酸总量的41.0%;苏氨酸、异亮氨酸、赖氨酸、色氨酸四种必需氨基酸接近FAO/WHO标准。此外,还含有丰富的矿质元素,如重金属镉、铅、砷、汞含量均在国家规定的食品安全标准以内。     

微波消解-电感耦合等离子体光谱法测定 铝塑包装奶粉中铝的含量

目的建立一种微波消解-电感耦合等离子体光谱仪器测定铝塑包装奶粉中铝的含量的方法。方法样品经微波消解并赶酸,采用电感耦合等离子体光谱(inductively coupled plasma emission spectrometry,ICP-AES)检测方法上机,通过样品中铝的信号强度和浓度成正比,对34种铝塑包装奶粉中的铝含量进行测定。结果该方法检出限为0.72 mg/kg,线性相关系数为0.9998,加标回收率为95.4%~98.6%。检测的34种铝塑包装奶粉中铝的残留量较少,均在低于0.72~1.28 mg/kg之间。结论该方法简便、快速、准确、所需样品量少,为奶粉的质量安全提供了技术保证。     

Shelf life prediction of aluminum foil laminated polyethylene packed vacuum dried coconut milk powder

Shelf life of vacuum dried coconut milk powder packed in aluminum foil laminated polyethylene packages was predicted using developed mathematical models based on two limiting criteria viz., onset of caking and lipid oxidation. Accelerated storage studies for coconut milk powder packed in aluminium foil laminated polyethylene pouches were conducted at 90 ± 1% relative humidity and 38 ± 2 °C temperature. Threshold value for the shelf life prediction based on moisture migration was taken as the critical moisture content at which lump formation was observed. Shelf life prediction based on lipid oxidation involved establishing relationships between rate of oxygen absorption, package oxygen concentration, volume of O₂ absorbed, peroxide value of the powder and storage time. A peroxide value of 10 mEq. of O₂ per kg fat was considered as the threshold limit for oxidative rancidity. A good fit between experimental and predicted data with relative deviation percent below 10% was observed during storage studies.     

ACCELERATED STORAGE, SHELF LIFE AND COLOR OF MANGO POWDER

Vacuum‐dried mango powder was produced from mango pulp through the addition of glycerol monostearate and tricalcium phosphate at 0.015 kg each per kg mango solids and maltodextrin at 0.62 kg per kg dry mango solids. The mango powder was packed in aluminum foil‐laminated pouches and stored in an accelerated storage environment maintained at 90% relative humidity (RH) and 38 ± 2C. The sticky‐point moisture content at 38 ± 2C was considered as the maximum moisture content to which the mango powder would remain stable. The shelf life of the powder predicted from this consideration and the Guggenheim‐Anderson‐de Boer (GAB) model for the water activity moisture content relationship was 114.68 days, whereas the actual shelf life was 105 days. The color change of the powder during storage followed first‐order reaction kinetics with a rate constant of 0.038 per day.     

Nutritional,antioxidant, and antimicrobial assessment of carrot powder and its application as a functional ingredient in probiotic soft cheese

Carrots (the main source of carotenoids) have multiple nutritional and health benefits. The objectives of this study were to evaluate the compositional, antioxidant, and antimicrobial properties of carrot powder and to examine its effect on the sensory characteristics, chemical properties, and microbial viability of probiotic soft cheese at a rate of 0.2, 0.4, and 0.6%. The carrot was turned into powder before being analyzed and incorporated as an ingredient in making probiotic soft cheese. Probiotic soft cheese was made from buffalo milk. The buffalo milk (～6.9% fat, 4.4% protein, 9.2% milk solids not fat, and 0.7% ash) was pasteurized at 75 ± 1°C for 5 min and cooled to 40–42°C. The milk was then divided into 4 aliquots. Sodium chloride (local market, Assiut, Egypt) was added at a ratio of 5% followed by starter cultures. The carrot powder (4.5% moisture, 4.8% ash, 2.7% fat, 8.2% protein, 11.9% fibers, and 72.3% carbohydrate) was added at a rate of 0.2, 0.4, and 0.6%, followed by addition of 0.02 g/kg rennet. The cheese was cut again into cubes, pickled in jars filled with whey, and stored for 28 d at 6 ± 1°C. The results of this study illustrated the nutritional and antioxidant properties of carrot powder. Incorporation of carrot powder in probiotic soft cheese affected the moisture and salt content at 0 d. The total bacteria count decreased from 7.5 to 7.3 log cfu/g in the cheese when carrot powder was used at a rate of 0.6%. The reduction of total bacteria count was noticed during the 28 d of storage by adding carrot powder. Furthermore, lactic acid bacteria and Bifidobacterium longum counts elevated with adding carrot powder during the 28 d of storage.     

The effect of multiwall Kraft paper or plastic bags on physico-chemical changes in milk powder during storage at high temperature and humidity

Plastic bags have recently been introduced as an alternative to multiwall Kraft paper bags in packaging milk powder in 25-kg sizes as it is thought that plastic bags are more durable and would preserve the quality of milk powders during storage better than paper bags. However, there is little scientific information available on the performance of plastic bags for milk powder storage. The aim of this study was to compare the properties of skimmed milk powder (SMP) packaged in plastic or paper bags. Commercially produced and packaged SMP in 25-kg plastic or paper bags was stored at 37°C and 90% relative humidity. Samples were analysed at intervals (0, 45, 90 and 135 days) for moisture, water activity, lactic acid content, pH, insolubility index, bulk density, flowability, dispersibility and particle size. The magnitude of change in the majority of SMP properties measured during storage suggests that plastic bags are similar to paper bags in maintaining milk powder quality during storage.